Marine propellers



'- April 5,1955 I J. M. LANGHAM. 3,244,235l

MARINE PROPELLERS Filed April 30, 1965 United States Patent MARHNEPROPELLERS John Michael Langham, 21 lieechcroft, Chislehurst, EnglandFiled Apr. 30, 1965, Ser. No. 452,128 Claims priority, application GreatBritain, May 4, 1964,

6 Claims. (Cl. 170-173) This invention relates to marine propellers.More particularly the invention is concerned with an improvedconstruction of amarine propeller enabling it to be easily removed fromits propeller shaft,

At present, it is standard practice for a marine propeller to be fittedto a shaft on a taper with a key and keyway to ensure that there is noangular movement. The propeller is driven up hard on the taper and isheld there by means of a conventional nut. Almost invariably to removethe propeller from the shaft it is necessary to heat the propeller bosscausing it to expand, releasing it from the shaft.

The known method has two disadvantages, firstly the fact of cutting akeyway in the shaft causes local stress raisers and leads to shaftfailure, particularly in large single screw vessel. Secondly, uneven andlocally intense heating of the propeller boss by external means oftengives rise to cracks which, in many cases, result in the propellerhaving to be scrapped. Furthermore, because of the differentcoeflicient' of expansion of the steel shaft and bronze and alloypropeller, it is common for the propller to slide along the keyway in alongitudinal direction when the ship and vessel is operating in waterswhere the temperature is greater than where the propeller was fitted.

An object of the invention is to overcome the above mentioneddisadvantages and provide an improved propeller construction whichenables the propeller to be readily removed from a propeller shaftwithout the risk of damage to the propeller or shaft.

A further object of the invention is to avoid the longitudinal movementwhich occurs due to the differential expansion.

The invention consists in a marine propeller comprising, an electricheating element, encased in refractory material embedded in thepropeller boss in the region of the shaft receiving bore of thepropeller, so that by passing an electric current through the electricheating element the said region of the boss is caused to expand in auniform and controlled manner.

Preferably the electric heating element comprises a helically woundresistance wire.

Alternatively the electric heating element comprises resistive trackingelements placed ininternal longitudinally drilled holes,

The invention will be further described by way of example with referenceto the accompanying drawings showing two preferred embodiments of amarine propeller, in which:

FIGURE 1 is an axial section through armarine propeller boss mounted ona shaft;

FIGURE 2 is a similar view to FIGURE 1 of a modified form of heatingelement;

FIGURE 3 is a similar view to FIGURES 1 and 2 of a second embodiment ofa marine propeller according to the invention.

Referring to the drawings the marine propeller illustrated in FIGURE 1comprises a boss I mounted on a shaft 2. The propeller boss 1 and theend portion of the shaft 2 on which the propeller is mounted aresuitably locked to provide a driving connection between the propellerand shaft, while the propeller is prevented from 3,244,236 Patented Apr.5, 1966 any axial movement by a power operated nut 3. This poweroperated nut 3 also serves to drive the propeller hard up onto thepropeller shaft when this has the conventional taper connection.

Cast into the propeller boss 1 in the region surrounding the shaftreceiving bore is a helically wound electrical resistance Wire 4 encasedin a covering of refractory material. This resistance wire 4 is lead outvia connections 5 in the end of the shaft 2 by means of which it can beconnected to an electrical supply.

To remove the propeller from the shaft 2 the nut 3 is removed and theconnections 5 are joined up to an electrical supply. A current is passedthrough the resistance wire 4 heating the propeller boss 1 and causingit to expand in a uniform and controlled manner sufiicient to releasethe propeller from the shaft, thus enabling the propeller to be easilywithdrawn from the shaft.

FIGURE 2 illustrates a modification of the heating element shown inFIGURE 1 in which the resistance wire 4 is set in an annular block ofrefractory material 6 located in a lightening chamber 7 formed in theboss 1. Other constructional features and the method of removing thepropeller from the shaft are the same as that described with referenceto the embodiment of FIG- URE 1.

A second embodiment of the invention is illustrated in FIGURE 3 in whichlike reference numerals have been used for similar components of thefirst described embodiment. In this second embodiment the helicallywound resistance wire 4 is replaced by a plurality of resistive trackingelements (not shown) which are placed in longitudinal drilled holes 8which run parallel to the shaft 2. These tracking elements are connectedto suitable terminal connections to which the electric supply isconnected for uniformly heating the propeller boss 1 for removing itfrom the shaft 2.

Various modifications may be made to the invention within the scope ofthe appended claims.

I claim: v

1. A marine propeller comprising, a propeller boss, an electric heatingelement and refractory material encasing the heating element which isembedded in the propeller boss in the region of a shaft receivingbore ofthe propeller so that by passing an electric current through theelectric heating element the said region of the boss is caused to expandin a uniform and controlled manner.

2 A marine propeller as claimed in claim 1, in which the electricheating element is in the form of a helically wound electricalresistance wire encircling the shaft receiving bore of the propeller.

3. A marine propeller as claimed in claim 2, in which an outer coveringof refractory material encases the electric resistance wire.

4. A marine propeller as claimed in claim 2, in which an annular blockof refractory material encases the electrical resistance wire and islocated in a lightening chamber formed in the propeller boss.

5. A marine propeller as claimed in claim 1, in which the electricheating element is in the form of a plurality of resistive trackingelements located in longitudinal holes drilled in the region of thepropeller boss surrounding the shaft receiving bore.

6. A marine propeller as claimed in claim 1, in which the propeller isdriven onto and retained against axial movement on the shaft by a poweroperated nut.

No references cited.

SAMUEL LEVINE, Primary Examiner.

E. A. POWELL, JR., Assistant Examiner.

1. A MARINE PROPELLER COMPRISING, A PROPELLER BOSS, AN ELECTRIC HEATINGELEMENT AND REFRACTORY MATERIAL ENCASING THE HEATING ELEMENT WHICH ISENBEDDED IN THE PROPELLER BOSS IN THE REGION OF SHAFT RECEIVING BORE OFTHE PROPELLER SO THAT BY PASSING AN ELECTRIC CURRENT THROUGH THEELECTRIC HEATING ELEMENT THE SAID REGION OF THE BOSS IS CAUSED TO EXPANDIN A UNIFORM AND CONTROLLED MANNER.